Disease Models & Mechanisms最新文献

Dominant variants in inosine monophosphate dehydrogenase 1 (IMPDH1), a key enzyme in the de novo synthesis of purine bases, cause progressive photoreceptor death, leading to blindness. To investigate the cause of degeneration, we generated the first mutant IMPDH1 animal models and expressed mutant forms of impdh1a in zebrafish cone photoreceptors. Unlike cones expressing exogenous normal impdh1a, cones containing impdh1a with the K238E mutation degenerated. Cones expressing impdh1a with the D226N mutation did not show significant cone loss by 2 years. Steady-state and flux metabolomics in zebrafish retinas revealed no differences in glucose shunting to the pentose phosphate pathway, no change in AMP or GMP due to D226N expression, but reduced AMP/IMP and GMP/IMP in K238E-expressing cones. cGMP levels were normal in both mutant retinas. Further, pde6cw59; impdh1asa23234 double mutant cones were not rescued from degeneration. Both K238E and D226N mutant-containing proteins formed abnormally large mislocalized filaments, which could disrupt normal dynamic protein-protein interactions. Our work disproves the model of a hyperactive enzyme leading to elevated cGMP causing cell death and reveals new defects associated with IMPDH1 mutant expression.

Duchenne muscular dystrophy (DMD) is a rare, progressive neuromuscular disease resulting from DMD variants, leading to loss of functional dystrophin. To evaluate human-targeted genetic medicines for functional dystrophin restoration, humanized genetic models containing the full human locus are required. This study characterized the hDMDΔ52/mdx mouse model previously reported by Pickar-Oliver and colleagues. Genomic characterization confirmed complete DMD duplication with identical exon 52 deletion junctions on both copies. Histological analysis showed increased diaphragm fibrosis and skeletal muscle central nuclei in hDMDΔ52/mdx mice versus hDMD/mdx controls. hDMDΔ52/mdx mice demonstrated reduced tibialis anterior specific force, decreased skeletal muscle fiber diameter, decreased resistance to eccentric contraction-induced damage and cardiac defects. Multiple serum biomarkers of disease were identified. Using a CRISPR/Cas9 gene-editing strategy to restore human functional dystrophin protein expression, detectable dystrophin expression in the heart and skeletal muscle and increased resistance to injury in the tibialis anterior muscle were observed. In summary, hDMDΔ52/mdx mice display multiple physiological and functional deficits associated with DMD pathology, which can be restored by human-targeted therapy, confirming the suitability of this model for developing human-targeted genetic medicines.

Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) is a rare, autosomal dominant neurodevelopmental disorder caused by pathogenic variants in NR2F1, characterized by developmental delay, intellectual disability, optic nerve anomalies and autism spectrum disorder. Most pathogenic variants cluster within the highly conserved DNA-binding domain (DBD) or ligand-binding domain (LBD) of NR2F1 and are associated with variable clinical severity, suggesting a genotype-phenotype correlation. Although previous mouse models have provided important insights, comprehensive behavioral characterization remains limited. Here, we present two novel BBSOAS mouse models harboring patient-specific variants in the DBD (Nr2f1+/R139L) and LBD (Nr2f1+/E397*), alongside the established Nr2f1+/- model. We analyzed brain morphology and behavior to further expand the murine phenotype and investigate the genotype-phenotype correlation. We demonstrate that these models recapitulate key aspects of the BBSOAS phenotype, including deficits in cognition, social communication and motor function, and that the presence and severity of behavioral abnormalities are dependent on variant type. Our findings provide new evidence for a genotype-phenotype correlation associated with domain-specific NR2F1 variants and establish a robust platform for future mechanistic and therapeutic studies.

Craniosynostosis is a multigenic congenital condition in which one or more calvarial sutures have prematurely fused during the development of the fetus. Pathogenic variants in FGFR2 are associated with the development of syndromic craniosynostosis, such as Crouzon, Apert and Pfeifer syndromes. Investigation of FGFR2-linked craniosynostosis is hindered by the lack of appropriate in vitro models. Patient-derived human induced pluripotent stem cell (hiPSC) in vitro disease models provide the opportunity to investigate the disease, identify molecular targets for pharmaceutical treatments, and enable the generation of autologous pluripotent stem cell catalogues. Here, we report three patient-derived hiPSC lines carrying the C342Y, S252W or E565G FGFR2 pathogenic variant. The patient hiPSC lines express characteristic pluripotency markers and display distinct phosphorylation profiles under unstimulated conditions. FGFR2C342Y showed autophosphorylation in the absence of bFGF ligand, although downstream docking proteins PLCγ and FRS2α were not phosphorylated. FGFR2S252W and FGFR2E565G hiPSCs showed increased phosphorylation of docking proteins PLCγ and FRS2α, whereas FGFR2 was not phosphorylated. These patient hiPSC lines provide molecular and cellular options to investigate FGFR2-linked craniosynostosis in the patient-specific genomic context and develop therapeutic modalities.

The mouse is a premier model system for investigating gene function and modeling human disease. For almost 40 years, Mouse Genome Informatics has worked to capture and integrate the data generated from mouse studies. A critical component of this integration is the development and use of the Mammalian Phenotype (MP) Ontology to capture the morphological and physiological effects of alterations to gene function in the mouse. As the wealth of phenotype data captured using the MP has expanded, its utility in the diagnosis of human disease has increased. Tools have been developed to use mouse and human phenotypes in variant identification. To enhance the applicability of the MP in disease diagnosis and increase the ability of researchers to find models for specific research questions, we have undertaken a disease-focused expansion of the MP. In addition, we have worked to improve the alignment of the MP to the Human Phenotype Ontology to make automated translation between mouse and human phenotypes easier and more reliable.

Neurodegenerative diseases, including polyglutamine diseases, remain a clinical challenge, partly because of limited animal models that recapitulate human disease. Here, we describe a second-generation transgenic marmoset model of spinocerebellar ataxia 3 (SCA3), a polyglutamine disease, which stably expresses expanded CAG repeats in ataxin 3 (ATXN3). All five offspring of the founder marmoset harbored the transgene with reduced transgene integration sites compared with the founder and without repeat instability or genetic mosaicism, offering improved construct validity. Three of the five marmosets developed progressive motor impairments that segregated into two distinct phenotypes - early onset with rapid progression and late onset with mild progression - accompanied by corresponding patterns in body weight gain and grip strength. Pathological analysis revealed cerebellar Purkinje cell loss, spinal cord neurodegeneration and widespread intranuclear inclusions. The severity of motor phenotypes correlated with transgene expression levels in disease-relevant brain regions, including the cerebellum and spinal cord. By overcoming the translational limitations of rodent systems, our second-generation model offers a powerful platform for investigating disease mechanisms and testing potential therapeutics, advancing the utility of transgenic marmosets as clinically relevant models of neurodegenerative diseases.

Huntington's disease (HD) is traditionally viewed as an age-related disorder. Emerging evidence suggests that mutant huntingtin (mHTT) disrupts early neurodevelopment, although the contribution of developmental alterations to the late disease onset remains to be clarified. Leveraging human pluripotent stem cell-derived brain organoids, we and others are exploring how mHTT affects the developing human brain. These models reveal impaired neural progenitor organization and function, accompanied by a mitochondrial stress response, indicating reduced capacity to manage cellular stress. Enhancing mitochondrial health and promoting neural cell resilience may thus represent potential strategies for improving the brain's compensatory mechanisms, thereby prolonging a healthy state. These insights highlight a potential window of opportunity for therapeutic interventions. Targeting mitochondrial fitness and neurodevelopmental pathways at early stages - long before clinical symptoms emerge - could help prevent or delay disease onset and progression in affected individuals.

Tremor is a common movement disorder associated with several neurodegenerative diseases, yet its mechanisms are not well understood. Using a machine-learning method, Feature Learning-based Leg segmentation and Tracking (FLLIT), we previously characterised gait and tremor signatures in a Drosophila model for spinocerebellar ataxia 3 (SCA3) and found them to be analogous to those in human SCA3. Here, we carried out a functional screen for neuronal populations that underlie tremor and found that dysfunction of a specific population of neurons in the ventral nerve cord (VNC) is necessary and sufficient for tremor. Adult-onset expression of mutant ATXN3 in, or genetic hypo-activation of, these neurons led to tremor, indicating their important role in adult motor control. RNA-sequencing and functional experiments showed that dysfunction of GABAergic neurons, and not that of other neurotransmitter populations tested, causes tremor. Finally, we identified a small subset of ∼30 predominantly GABAergic neurons within the adult VNC that are essential for smooth walking. This study demonstrates that tremor in SCA3 flies arises from GABAergic dysfunction, and that FLLIT can be used to dissect motor control mechanisms.